1. Field of the Invention
The present invention relates to a roll feed apparatus of type in which a pair of rolls clamps a strip therebetween to intermittently feed the strip by a constant length into manufacturing machines such as a press machine or the like.
2. Description of the Prior Art
A roll feed apparatus of the type referred to above is known, which comprises a drive shaft driven rotatively, a pair of first and second roll shafts and a pair of first and second rolls mounted respectively on the first and second roll shafts for swinging movement therewith. A swingingly driving device is provided for converting the rotative motion of the drive shaft to swinging motion of the first and second rolls. The first and second rolls cooperate with each other to clamp therebetween a strip to transport the same when the first and second rolls are moved swingingly by the swingingly driving device in a strip transporting direction. A roll release device is provided for moving the first and second rolls aways from each other when the rolls move swingingly in a direction opposite to the strip transporting direction, to release a clamping force applied to the strip by the first and second rolls. A strip braking device is provided for applying brake to the strip to fix the same for a period during which the rolls do not transport the strip. Such type of roll feed apparatus is disclosed, for example, in Japanese Utility Model Application Laid-Open No. 59-130831 (Utility Model Application No. 58-24892), Japanese Utility Model Application Laid-Open No. 59-130832 (Utility Model Application No. 58-24893), Japanese Utility Model Application Laid-Open No. 61-32510 (Utility Model Application No. 59-114306) and the like.
If the roll feed apparatus of the type described above is employed in combination with, for example, a press machine, the first and second rolls become stationary after having fed the strip by a constant strength into a die assembly of the press machine. After having become stationary, that is, for the period during which the rolls do not transport the strip, the rolls are moved away from each other by the roll release device, and the strip is fixed by the strip braking device. Under such condition, the rolls are moved swingingly in the direction opposite to the strip transporting direction. During this period of swinging motion of the rolls, press working is effected on the strip fed into the die assembly while the strip is fixed by the strip braking device.
The above-described conventional roll feed apparatus has such a problem that it might not accurately position a strip in manufacturing machines such as a press machine or the like. Specifically, some types of the press machines comprise a die assembly in which pilot pins project downwardly from a lower surface of an upper die, and are adapted to be inserted respectively into receiving holes formed beforehand in the strip when the upper die and a lower die are brought into engagement with each other to perform press working, whereby the strip can accurately be positioned in the die assembly. In the above-described conventional roll feed apparatus, however, since the strip is maintained fixed by the strip braking device when the upper and lower dies are brought into engagement with each other to perform press working, it is impossible for the pilot pins to position the strip if slight positional displacement or shift exists between the pilot pins and the receiving holes in the strip fed into the die assembly. Thus, there are anxieties that the positioning is not performed accurately, causing a deformation of the strip and a damage or breakage of the dies.